What to do with a spider bite to prevent infection?

Depends: Most spider bite are like other insect bites and may hurt at first but afterward, like with any break in the skin, infection needs to be watched for. So cleaning is best. Some are dangerous like the well known widow and recluse bites in the usa, but there are other less known species that can cause problems like the recluse too. Generally, watch the bite and if concerned, see a physician.

Clean wound: Use simple soap and water. There is nothing better than this.